You can search for guides on Nextstop by places, guides, and map, or just focus your search on a specific city. The site was in closed beta until today, which helps explain why a good number of my NYC recommendations included more obvious tourist spots (think Statute of Liberty) and less off-the-beaten-path selections. Of course, if and when more users create their own guides, the site could potentially be a decent resource for interesting things to do in a given city, especially centered around a specific theme.